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Low affinity of Trypanosoma brucei transferrin receptor to apotransferrin at pH 5 explains the fate of the ligand during endocytosis
Author(s) -
Maier Alexander,
Steverding Dietmar
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)01073-3
Subject(s) - trypanosoma brucei , endocytosis , transferrin receptor , transferrin , receptor , endocytic cycle , biochemistry , ligand (biochemistry) , receptor mediated endocytosis , microbiology and biotechnology , dissociation constant , biology , chemistry , gene
Uptake of host transferrin (Tf) in Trypanosoma brucei is mediated by a heterodimeric, glycosyl‐phosphatidylinositol‐anchored receptor. After endocytosis, Tf is delivered to lysosomes where it is proteolytically degraded. So far, the sequence of events leading to ligand dissociation and degradation is undefined. We now show by Triton X‐114 phase separation that iron‐free Tf (apo‐Tf) dissociates from the receptor at pH 5.0. The low affinity of apo‐Tf for its receptor at pH 5.0 is confirmed by an apparent dissociation constant of 1.1 μM. The implications of this result on the mechanism of intracellular processing of Tf in trypanosomes are discussed.